Cathode-ray apparatus



Dec. 14 1948. R GETHMANN 2,456,399

CATHODE-RAY APPARATUS Filed Oct. 24, 1945 v 2 Sheets-Sheet 1 Inventor:

Richar-d B.Get hmann His Attorney.

Dec.'14, 1948. Y R. B. GETHMANN I CATHODERAY APPARATUS 2 Sheets-Sheet 2Filed 001;. 24, 1945 F/gaf F/QA.

umunumnmi Irfivehtofp bym' 2% H IS Att orn ey.

n a m h t e B d r a h Patented Dec. 14, 1948 or to General Electric ofNew York Company, a corporation Application October 24, 1945, Serial No.524,275

1 Claims. (01. 250-161) This invention relates to electron dischargedevices of the cathode ray type and particularly to apparatus forcontrolling the direction and de' flection of the electron beams of suchdevices.

Apparatus employing cathode ray tubes nor- I in electron gun and as aresult the tubes donot produce their cathode ray beams in the sameposition and direction. It is therefore apparent that when one tube issubstituted for another in the apparatus it becomes necessary toadjustthe direction of the electron beam, and devices are commonly providedwhich make it possible to adjust the direction of the beam so that thespot on the flourescent screen of the cathode ray tube appears at thedesired position. However, an accurate display of the signal impressedon a cathode ray tube may be prevented because of undesirable deflectioncomponents of the magnetic field associated with the magnetic deflectionand focus coils. The distortion of the signal due to these componentscan be minimized by bringing about a coincidence of the axes of thedeflecting and focus coils and the 'axis' of the electron beam.Accordingly it is an object of this invention to provide in an electrondischarge apparatus of the cathode ray type an improved arrangement formounting the deflecting .coils and the focusing coil in their positionsabout th envelope of a cathode ray tube.

It is another object of this invention to provide an electron dischargeapparatus of the'cathode ray type including an improved arrangement foradjusting the position of the electron beam and for securing coincidenceof the axes of the focusing and deflecting coils and of the beam.

The novel features which are believed to be characteristic of thisinvention are set forth with. particularity in the appended claims. Theinven= tion itself, however, both as to its organization and method ofoperation, together with further objects and advantages thereof, maybest be understood by reference to the following description taken inconnection with the accompanying drawings in which Fig. 1 is a sideelevation view, partly in section, of a cathode ray apparatus embodyingthis invention; Fig. 2 is an enlarged view,partly in section, of aportion of the apparatus shown in Fig. 1; Fig. 3 is a sectional view onthe line 33 of Fig. 2; and Fig. 4 is a sectional view on the line 4 --4of Fig. 2.

Cil

Referring now toFig. I, a cathode ray tube I having a glass envelopecomprising a bowlyportion 2 and a neck portion 3 is mounted on asuitable supporting base indicated by the line 4- on a split collar 5secured to a supporting member 6 and with the'bowl portion held in asupport 'Lby an insulating-collar 8 of rubber or other suitableresilient material. -A glass viewing screen 9 is secured inthe collar 8so that it lies over the face of the cathode ray tube I. A suitablehousing 10 is mounted on the support I and encloses the bowl 2; thishousing is also attached to the support 6 through adjusting rods H. Thecathode ray tube I is provided with suitable electrodes constituting anelectron gun for projecting a cathode ray beam against a fluorescentscreen covering the inner face of the bowl 2 adjacent the viewing screen9. The details of construction-of the elementsof the electron gun arenot essential to an understanding of this invention and have not beenillustrated. However, a portion of the first anode of the electron gunis indicated at: I2 in Fig. 2. In order to bring the electron beam tofocus on the luminescent screen of the tube; a focusing coil [3 ismounted about the neck 3 of the tube between the anode-I2, which isnearithe source of the electron beam, anda'set of deflecting coilsindicated at M. The details of construction of the focusing coil I3 andof the deflecting coils M have'not been shown as these coilsmay beconstructed in any suitable manner for providing magnetic fields fordeflecting and for focusing the cathode ray beam. When the tube l isfirst placed in the supporting structure it is necessary to adjust thealignment of the cathode ray beam so that it is projected longitudinallyof theneck 3 onto the screen in the desired direction. In order toadjust the direction of the electron beam there is provided an annularpermanent magnet 15;

which may be rotated about the neck 3 of the tube. This magnet isrotatably mounted on a nonmagneticring l6 which is clamped about anextended nonmagnetic sleeve I1, attached to the collar-5. The magnet l5has a single air gap indicated at I8 and is so magnetizedthatjit pro-'-,

duces a field extending diametrically across-the ring; thus, when theringis rotated, the direction of the field is also rotatedl- It will beapparent that when the ring is rotated the direction of. the electronbeam is rotated. By rotating the ring l5 the beam may be moved throughany angle into the desired position. In order to adjust the angle of thebeam with respect to the longitudinal axis of the tube, the strengthoffthe field produced by t been? is se e We e efie eit eas tron gun. Thering [6 which carries the gmag netic ring I5 is clamped about thesupporting sleeve I! by a ring clamp 2|! provided with .a

clamping thumb screw 2!. i The supporting ring I6 is provided with aplurality of longitudinal slots 22 extending from the seat-of the magnet1:5 through the right-hand edgeof the support thereby forming aplurality of separate finger portions which may be clamped tightly aboutthe sleeve -11. *The supporting ring lG :may be elamped inany positionon the sleeve 11 ito select the :position of the magnet 'liaxially-ofthe tube andwith respect to the sleeve I8. The-direction ofthe beam may also be adjusted :by changing ilongitudinal position of thecylinder 5 with 351 851180? to the anode #2 to effecta simultaneouschange in the positions =of the ring 15 and the core H withrespecttothe:anodedi. One or more openings 23 :may be provided in the sleeve 11to afford a view -oi the position of the anode 42 of the tube when thering and sleeve assembly is being 'adjusted with respect-toithe anode.

1f theaxis f the deflecting coil *3 and-of the beam projected'within thetube do not coincide, then waria'tlons in the focusing field result indistortion-of the signal as it'appears on the fluoresoent screen.similar situation prevails 'with respectto the deflecting coils I4, andit is desirable that the "central axis of the-deflecting coils andofthefocusing coilcoincidewiththe axis of theelect-ron beam. ;'In ordertosecure this result the deflecting and focusing coils are secured togather on 'a common :mounting'collar 24 to provide a unitary assemblyarranged so that the central magneticaxes Of thecQiIs-are-in alignmentand extend -in the direction iii-which the cathode raybeam'is to beprojected. The coils are spaced fromthe-tube neck 3' and thecollarrZl-is-attached to the'supportingstructure 6 by a -moun'ting whichpermits adjustment -of the collar 24 lateraiiykof the tube neck 3 atright angles to therequired axis of the beam. This mounting ineludes -amountingpl-ate 25 whichis supported on the structure -B through theagenoyof an intermediate plate 16. "The plate 2-5 is clampedto thecollin- 24 byturning set screwsfil shown in Fig. 3 until they press twosplit segments '28 tormed on the platen into engagement with the collar24. clearly shown {in Fig. 3 the -mount-ing plate 25 *is slidabl-ymounted with respect to the inter mediate plate 28 it "being providedwith four ho on a s otsfl o e eac co er cf the-p a e 2.5 ans wnieh nga tb sc ews {50 a t ched tothe plate 25 {or clamping-the plates 35 anddfitogether. Adinstme tof th -pla efi w th resp c toth plat -fi-is aii ddby l se in the thum screws a d en tu n ng a thumb screw 3,!

mnunted inlugsfl and onthe iateszs and 26,.

slotsflbe' gp o ded init p a 25 and thumb sc ws, 5 on th s p o t ngstruct re '5,- The plate 16 maybe slidably moved with respect to thesupporting structure 6 by loosening the thumb screws 35 and then turninga thumb screw 36 mounted in lugs 31 and 38 on the plate 26 and support6, respectively. The slots 29 are at right angles to the slots 34 andthus the position of the collar 24 and of the coils carried thereby maybe adjusted laterally in any direction at right angles to thelongitudinal axis of the tube neck .3. This lateral adjustment makes'it'possible to move the common central magnetic axis of the deflectingand focusing coils into any selected position; and

afiincethis axis extends in the direction in which the cathode ray beamis to be projected, the axes of :thecoils and-of th'e beam may bebrought into coincidence.

The focusing'coil i3 is provided with a flanged boss or collar :39 whichfits closely within the collar 24 and is secured thereto by a pluralityof setkscrews 40. The focusing coil may be removed from the collar byloosening the set screws and sliding .the ibos-s -39 v=out of the collar:24. This construction.afiordseasyassembly ofzthe focusing anddeflecting coil unit, and thefit of the collar 39 within the .collar 12Ais such thatualignment .oi the axes of .ithe :focusing :and deflectingcoils is assured .when thecollar :has been tightened rin place byitheset screws.

twhenia cathode ray tube is :to be installed iin the apparatusillustrated, -:the resilient collar .8, stogether with a metalframe-structure indicated .atidl and :the glass.=screen:,zisfittedloyersthe face of .the bowl I2 :of the tube. The tube :is then1111- serted in :the apparatus so :that ail; :rests on the flower:portion :of the support 1. 5. As iswolearly shown Ei-n Rig. {4, stheupper portion of it-he support 5 is :removable from the lower :portionEby tloosenring .two set =scre.ws :42 which are :secured to 'the lower:portion and. :enter .=slots A3 ii-n :the upper removable portion. Twopadsdidzof vrubber orrother suitable material are cemented *totthe upper:and ;lower portions :of :the support The-upper .porliiOH'rOf :theclampifi is then-.placedmver the neck of thestube, aslshown in Fig. 14.The iframe 1H ,is thenqsecured ,ein place -.on the sup-port -I :so thatthe face of :the tube is in sitszdesiredposition with the'longitudinalaxis of the neck of the tube substantiallyparallehtlo theaxisofvtlierdeflecting and focusing unit. The tube :is adjustedlongitudinaliy of its support .bymeans -of rods d1 until the gun 1.2 isin its rrequiredcposition as determined bysighting through :one :of theopeningslld. The clamping screws 112 i are then rtightened to hold theupperzportion of the clamping (member 5 in position about the tube meekand thereby maintain the'itube in its :desired position with respect tothe magnetic ring 1-5. The [electrical onnections idiot-shown) :are thenmade so that "for purposes of testing :there may be applied-to thefocusing -coil either an alternating current or a direct currentxwhichcan lie-switched to be negative, aerobi -positive. The tube-is'thenexcited to generate-the electronbeam and if 'the axis'of the focus coiland the beam do-not coincide a pattern will appear on the screen whenalternating current isa-pplied to the *focus coil or the position of thebeam will be shifted upon switching the direct current of the focuscoil. This pattern or shifting of the beam is produced by ;a changeinintensity and'direction of the focusing field during eachalternatingcurrentcycle or during eachchange in direction or intensity of thedirect current. The pattern may be changed by rotatingithemagnetic ring15 and by shifting it axially and also'by shifting the position of thefocusing and deflecting coil unit. It will be round that by adjustmentof these devices the pattern produced by the beam maybe reduced to a dotin the case "of' alternating testing current, and in the case of directcurrent the threedots corresponding to the three switching positions maybe caused to coincide. This positionof coincidence occurs whenthedirection of the beam is parallel to the axis of deflection of thefocusing coil and coincidencetherflwith. Adjustment of the intensity oftheifield produced by the magnetic ring 15 may, of course be made byaxial movement of the core [9 during 'the adjustment. When the desiredposition for the magnetic ring on the tube I! has been determined, thethumb screw 2| is tightened to maintain lthat position. 1 In a similarmanner the'f'ocusing and deflecting coil assembly is retained in itsfinal desired position by tightening the thumb screws 30 and 35.

By constructing the supporting structure and the focusing and deflectingcoils so that coincidence of the beam and coil axes may be secured,distortion of the signal portrayed on the screen is minimized. There isminimum astigmatism, and changes in the position of the spot resultingfrom random changes of focusing coil current are minimized. In cathoderay apparatus, utilizing the position of the luminescent spot on thescreen as a measure of current, the coincidence of the coil and beamaxes assures minimum error of the measurement.

While the invention has been illustrated in connection with a particulartype of cathode ray tube, other applications and embodiments of theinvention will readily be apparent to those skilled in the art. It isnot, therefore, desired to limit the invention to the specificconstruction illustrated and described, and it is intended by theappended claims to cover all modifications which fall within the spiritand scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In an electron discharge apparatus of the cathode ray type includingan envelope having therein a screen and an electron gun for projecting acathode ray beam onto the screen, a magnetic focusing means arrangedabout the axis of the beam and having its central axis extending in thedesired direction of the beam, means near the origin of the beam foradjusting the direction of the beam to make it parallel to the centralaxis of said focusing means, and means for moving said focusing meanstransversely of the direction of said beam for bringing the central axisof said focusing means into coincidence with the axis of said beam.

2. In an electron discharge apparatus of the cathode ray type includingan envelope having therein a screen and an electron gun for projecting acathode ray beam onto the screen, a magnetic focusing coil arrangedabout the axis of the beam and having its central axis extending in thedesired direction of the beam, means providing a rotatable magneticfield about the beam near the origin thereof for adjusting the directionof the beam to make it parallel to the central axis of said focusingcoil, and means for moving said coil transversely of the direction ofsaid beam for bringing the central axis of said coil into coincidencewith the axis of said beam.

3. In an electron discharge apparatus of the cathode ray type includingan envelope having therein a screen and an electron gun for projecting acathode ray beam onto the screen, a magnetic focusing means arrangedabout the axis of the beam and having its central axis extending inthedesired direction of'the beam, a beam (1e; fleeting means arranged about'said envelopebe' tween saidfocusing means and said screen, saiddeflecting means being fixed with respect to said focusing means andhaving its central axis in alignment with 'the'central axis of saidfocusing means, means near the origin of the beam for adjusting thedirectionof the beam to make it parallel to the central axis of saidfocusing means, and means for moving said focusing and deflecting fmeanstransversely of the direction of said beam for-bringing thecentral axisof said focusing and deflecting means into coincidence with the axis ofsaid beam.

4 In an electron discharge apparatus of the cathode ray type includingan envelope having therein a screen and an electron gun for projecting acathode ray beam onto the screen, a magnetic focusing coil arrangedabout the axis of the beam and having its central axis extending in thedesired direction of the beam, a deflecting coil assembly arranged aboutthe axis of the beam between said focusing coil and said screen andhaving its central axis in alignment with the central axis of saidfocusing coil, said focusing and deflecting coils being secured togetheragainst relative movement therebetween, means providing a rotatablemagnetic field about the beam near the origin thereof for adjusting thedirection of the beam to make it parallel to the central axis of saidfocusing coil, and means for moving said focusing and deflecting coilstransversely of the direction of said beam for bringing the central axisof said coils into coincidence with the axis of said beam.

5. In an electron discharge apparatus of the cathode ray type includingan envelope having therein a screen and an electron gun for projecting acathode ray onto the screen, a support for said envelope, a magneticfocusing coil and a magnetic deflecting coil secured together and havingtheir central axes in alignment in the direction of the beam, means nearthe origin of the beam for adjusting the direction of the beam intoparallelism with said central axes, and means for mounting said coils onsaid support and for affording movement of said coils together bodilylaterally of the beam whereby the axis of said coils may be moved intocoincidence with the axis of said beam.

6. In an electron discharge apparatus of the cathode ray type includingan envelope having therein a screen and means for projecting a cathoderay beam onto the screen, means for supporting the envelope, a focusingand deflection coil unit surrounding the envelope and attached to thesupporting structure, said unit being positioned with its central axisparallel to the desired axis of the cathode ray beam, means near theorigin of the beam for adjusting the direction of the beam intoparallelism with said central axis, and means affording movement of saidunit laterally while maintaining said central axis in the same directionfor moving said central axis into coincidence with the beam.

7. In an electron discharge apparatus of the cathode ray type includingan envelope having therein a screen and means for projecting a cathoderay beam onto the screen, a supporting structure, a unitary assemblycomprising a focusing coil and a deflecting coil having a common centralaxis, means near the origin of the beam for adjusting the direction ofthe beam into parallelism with said central axis, said assembly beingarranged to .fit lover the -nvelope :in ,spaced relatien thezeto landwith said common,.axis extendvsaid uni-tmay be .brought into coincidencewith the cathode ray beam. 3

' RICHARD .B. 'GE'THMANN.

REFERENCES mum The following orefgrences .are of .record in the file ofthis patent:

Number lflumbr UNITED STATES PATENTS Name Date Kuelmi Dec. 14, 1937Goldsmith Decif31, 1940 De Tar Mar. 11,1941 Schuchmann et a]. Dec. 15,1942 Packer Nov. '27, 1945 FOREIGN vZPA'IEE'NTS Country Date GreatBritain Sept. 13, 193'!

